stopOnFailure and localhost > 127.0.0.1

`stopOnFailure="true"` because Travis CI doesn't stop a failing test otherwise.

`<const name="WEB_SERVER_HOST" value="127.0.0.1" />` because there could be problems using `localhost`. (e.g. Travis CI and my testing environment don't work using `localhost`)
Added `.travis.yml` for CI using Travis.